Double-Sided Flap Disc for Use with a Mounted Grinder

ABSTRACT

A double-sided flap disc for use on a mounted grinder. A carrier plate has abrasive flaps attached around its outer perimeter on both sides. The flaps are arranged so that each side mirrors the other, that is, the flaps attached to one side face clockwise and the flaps attached to the other side face counterclockwise. This allows a U-shaped workpiece, such as a horseshoe, to be moved side to side against both sides of the disc, to provide symmetrical grinding.

TECHNICAL FIELD OF THE INVENTION

This invention relates to power tools, stationary or portable, and moreparticularly to abrasive wheels and discs used with bench orfloor-mounted grinders.

BACKGROUND OF THE INVENTION

A bench grinder is a benchtop type of grinding machine used to driveabrasive wheels. A pedestal grinder is a similar and usually largerversion of grinder that is mounted on a pedestal and stands from thefloor. These grinders have removable grinding wheels and are used tohand-grind various workpieces. Bench grinders can be mounted at apermanent location in a shop or carried on a mobile platform such as awork truck.

Examples of conventional uses of bench grinders are sharpening cuttingtools and shaping metal pieces. Bench grinders are standard equipment inmetal fabrication shops and machine shops.

Bench and pedestal grinders are designed for placing the workpieceagainst the periphery of the grinding wheel. Conventional bench grinderwheels are designed for grinding on the periphery only. “Side grinding”on a bench grinder wheel is considered to be unsafe and runs the risk ofwheel explosion.

The grinding performed on the periphery of a grinding wheel of a benchgrinder is in contrast to grinding with a “disc” of a handheld grinder,such as an angle grinder. These tools are designed to do grinding on oneside of the disc. The workpiece is in a secured fixed position, such asin a vice. The handheld grinder is held in the operator's hands, and theoperator presents and uses the grinding disc at an angle to theworkpiece.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a horseshoe as an example of a workpiece with whichthe invention is used.

FIG. 2 illustrates a grinder having a double-sided flap disc inaccordance with the invention.

FIGS. 3 and 5 are plan views of the double-sided flap disc.

FIG. 4 is a side view of the double-sided flap disc.

FIG. 6 is a perspective view of the double-sided flap disc.

FIG. 7 illustrates the double-sided flap disc in use for grinding theinside heel portions of a horseshoe.

DETAILED DESCRIPTION OF THE INVENTION

This description is directed to a “double-sided flap disc” for use witha bench or pedestal grinder. As explained below, the double-sided flapdisc has abrasive flaps on both sides. It is designed for situations inwhich it is desired to have a stable grinding surface on two sides of arotating disc.

An example of use of the double-sided flap disc is in farrier work,where the farrier shapes the heel portion of a horseshoe by grinding thehorseshoe on the inside of both ends. The farrier holds the horseshoewith the open end presented to the grinder and moves the horseshoe fromside to side during grinding to ensure a symmetrical result.

As stated in the Background, conventional bench grinders and pedestalgrinders have a grinding wheel and are designed for grinding on theperiphery of the wheel. In contrast, hand-held grinders have thinnerdiscs that are designed for grinding on one side.

For purposes of this description, bench and pedestal grinders arereferred to as “wheel-type” grinders as distinguished from hand-heldgrinders. A particular advantage of a wheel-type grinder is that it ismounted on a secure platform and thereby provides a stable grindingsurface. The operator may easily hold the workpiece in hand whileproducing the desired shape or surface with the grinder.

FIG. 1 illustrates a horseshoe 10 having heel portions 10 a that havebeen ground to a desired shape on the inside of each end. In particular,the end of each heel portion has been ground away to form an angledinside corner, A. The material removed is indicated by the dotted lines.

In conventional farrier work, the horseshoe 10 must be awkwardly andunsafely held against the wheel periphery of a bench grinder. However,as explained below, the double-sided flap disc of this invention makesthis task much safer, easier, and accurate.

FIG. 2 illustrates a grinder 20 having a double-sided flap disc 22 inaccordance with the invention.

Grinder 20 is a “mounted” grinder, in the sense that it is not hand-heldand is mounted on a platform 21. Various means such as bolts are used tosecurely mount grinder 20 to platform 21.

Grinder 20 may be any one of various commercially available wheel-typegrinders but adapted for use with disc 22. Conventional bench grindersare characterized by having removable and replaceable grinding wheels.However, in FIG. 2, the grinding wheel has been replaced by adouble-sided flap disc 22. Alternatively, grinder 20 may be specificallydesigned for mounting disc 22 and for use with the side grindingapplications described herein.

Grinder 20 is powered by an electric motor (not shown), which drives anarbor 25 (also sometimes referred to as a spindle) that rotates. Themotor is housed within a durable rigid housing 27. Grinder 20 furtherhas various control features and power connections (battery or linevoltage) such as are found on conventional grinders.

Disc 22 is mounted on arbor 25, typically by having a center hole whichis slid onto the end of arbor 25. Disc 22 is securely attached so thatit rotates as arbor 25 rotates and resists pressure applied to disc 22by a workpiece being held against it during use. A nut 26 holds disconto arbor 25 and facilitates removal and replacement of a disc 22 whenit becomes worn from use.

In the example of FIG. 2, platform 21 is part of a mobile workshop, suchas might be used by a farrier. Farriers commonly use such mobileworkshops, often configured as vans with back doors that open to alloweasy access to grinders, forges, and other equipment for shoeing horses.However, the invention is not limited to this application and is usefulfor any mobile or stationary application where a grinder is desired tobe used for abrading a workpiece.

In operation, flap disc 22 is quiet, long lasting, and smooth running.It allows for stock removal (abrading) of metals or other hardmaterials, using both sides of the disc 22. The object to be ground maybe held in the operator's hand. Using both sides of disc 22, theoperator can grind areas of objects, such as the inside heels of ahorseshoe as shown in FIG. 1, that are not accessible when usingconventional grinding wheels. In particular, workpieces having complexshapes such a “U” shape are not accessible with existing wheels forbench grinders but are accessible to grinder 20.

A feature of the invention is that the arbor 25 of grinder 20 issufficiently long to allow disc 22 to be spaced a distance from the bodyof grinder 20. Specifically, disc 22 is typically mounted withsufficient space between disc 22 and the main body of grinder 20 so asto allow a workpiece to be moved back and forth horizontally relative tothe plane of disc 22. Various bushings and bolts may be used to varythis distance if desired, as well as to adjust the size of the centralhole in disc 22 to the diameter of arbor 25.

Depending on the application and expected dimensions of the workpiece,disc 22 is expected to be mounted along arbor 25 at least two inchesfrom the main body of grinder 20. For example, where the workpiece is ahorseshoe, allowance for several inches of side-to-side motion of theworkpiece is desired. This is in contrast to conventional benchgrinders, where a minimal gap between its grinding wheel and the body ofthe grinder is desired.

FIG. 3 is a side plan view of double-sided flap disc 22, removed fromthe grinder 20. FIG. 4 illustrates the outer periphery of a portion ofdouble-sided flap disc 22. FIG. 5 is an additional side plan view, andFIG. 6 is a perspective view.

Double-sided flap disc 22 comprises a carrier plate 30 to which areattached abrasive “flaps” 31 on each side. Carrier plate 30 is planar,round, and flat on both faces. In the example of this description,carrier plate 30 has a diameter of 7 inches, which is the same as thediameter of the grinding wheels for which many conventional benchgrinders are designed. However, carrier plate 30 may have otherdiameters for varying sizes of grinders. The carrier plate 30 may bemade from a variety of rigid and strong materials, with a suitablematerial being fiberglass.

In the example of this description, carrier plate 30 is 0.125 inches inthickness. Other thicknesses may be used. Because the function ofcarrier plate 30 is for attachment of flaps 31 and not for grinding, itneed only be sufficiently thick to provide structural support for flaps31.

Carrier plate 30 has a center hole, which is sized so that carrier plate30 may be slid onto the arbor of grinder 20. In the example of thisdescription, center hole is 0.6250 inches. However, like the diameter ofthe carrier plate, the size of the center hole may vary to fit aparticular type or size of grinder. The center hole allows disc 22 to bemounted onto the arbor 25 of the grinder using appropriate nuts,flanges, and bushings.

Around the perimeter of both sides of carrier plate 30 are arrangedindividual pieces of overlapping abrasive sheets known as “flaps” 31.Each flap is a cloth polyester backing, known as X or Y type, coatedwith abrasives. Examples of suitable abrasives for flaps 31 are ceramicalumina, aluminum oxide, or zerconia alumina in grit sizes 36 to 60.

In the example of FIGS. 3 and 4, the double-sided flap disc 22 hasapproximately 96 flaps on each side. The size of each flap is 1.26inches by 0.991 inches, more or less. Typically, the flaps 31 arerectangular and of uniform size. However, other shapes may be used. Theflaps 31 are sufficiently thick to provide a durable abrasive surfacefor repeated use to grind the material for a particular application. Theflaps 31 may be attached to carrier plate 30 using adhesives or otherattachment means.

If disc 22 is viewed toward on side, mounted on a grinder, the flaps 31are attached to carrier plate 30 overlapping each other in a clockwisedirection. Looking at the left side, the flaps are attached to carrierplate 30 overlapping one another in a counterclockwise direction.

In other words, and as particularly shown in FIG. 4, each flap 31 can beconsidered to have an attached edge and a free edge opposite theattached edge. When the disc is viewed toward its flat sides, the freeedges on one side of carrier plate 30 face in the opposite angulardirection (clockwise vs counterclockwise) as the free edges on the otherside of carrier plate 30.

Referring to FIG. 4, when viewed toward the periphery, the flaps on eachside of the disc have their free edges running in the same direction.This allows two inner elements of a workpiece, such as the two open endsof a horseshoe, to be moved from side to side during grinding to producesymmetrical shapes.

The degree of overlap of flaps 31 may vary. In the example of thisdescription, the flaps edges are close together for a large degree ofoverlap, such that the flaps are lifted from the surface of carrierplate at about 45 degrees.

The flaps completely surround the circumference of carrier plate 30 oneach side but need cover only the outer perimeter of carrier plate 30 oneach side. The coverage of flaps 31 toward the center of the disc mayvary. In the example of this description, the flaps 31 coverapproximately the outer edges of carrier plate 30 inward about ⅓ of theradius of carrier plate 30.

FIG. 7 illustrates a portion of double-sided flap disc 22, assumed to bemounted on grinder 20. When disc 22 is rotating, a horseshoe 71 may beheld by hand and presented with its open end toward disc 22. Thehorseshoe may be manually moved from side to side so that both innercorners of the horseshoe may be shaped. Other workpieces requiringgrinding on two opposing sides may be abraded in a similar manner.

What is claimed is:
 1. A double-sided flap disc for use on a mountedgrinder, the grinder having a rotating arbor, comprising: a carrierplate made from a planar rigid material and being round with a flat faceon both sides; wherein the carrier plate has a center hole suitable foruse in mounting the disc on the arbor; on each face of the carrierplate, a series of abrasive flaps arranged around the outer perimeter ofthe carrier plate; wherein each flap is attached to the carrier platealong a fixed edge of the flap that is opposing a free edge of the flapand such that the flaps are overlapping; and wherein the flaps attachedto one side have their free edges facing clockwise and the flapsattached to the other side have their free edges facingcounterclockwise.
 2. The double-sided flap disc of claim 1, wherein thegrinder is a bench or pedestal grinder.
 3. The double-sided flap disc ofclaim 1, wherein the disc is spaced along the arbor with a gap of twoinches or more from the body of the grinder.
 4. A method of using amounted grinder, the grinder having a rotating arbor, comprising:attaching a double-sided flap disc onto the arbor, the double-sided flapdisc having: a carrier plate made from a planar rigid material and beinground with a flat face on both sides; wherein the carrier plate has acenter hole suitable for use in mounting the disc on an arbor of thegrinder; on each face of the carrier plate, a series of abrasive flapsarranged around the outer perimeter of the carrier plate; wherein eachflap is attached to the carrier plate along a fixed edge of the flapthat is opposing a free edge of the flap and such that the flaps areoverlapping; and wherein the flaps attached to one side have their freeedges facing clockwise and the flaps attached to the other side havetheir free edges facing counterclockwise.
 5. The method of claim 4,wherein the grinder is a bench or pedestal grinder.
 6. The method ofclaim 4, wherein the attaching step is performed such that the disc isspaced along the arbor with a gap of two inches of more from the body ofthe grinder.
 7. A grinder, comprising: a grinder housing; means formounting the grinder on a platform; an electric motor inside thehousing; an arbor driven by the motor such that it rotates; adouble-sided flap disc mounted on the arbor, the double-sided flap dischaving: a carrier plate made from a planar rigid material and beinground with a flat face on both sides; wherein the carrier plate has acenter hole suitable for use in mounting the disc on an arbor of thegrinder; on each face of the carrier plate, a series of abrasive flapsarranged around the outer perimeter of the carrier plate; wherein eachflap is attached to the carrier plate along a fixed edge of the flapthat is opposing a free edge of the flap and such that the flaps areoverlapping; and wherein the flaps attached to one side have their freeedges facing clockwise and the flaps attached to the other side havetheir free edges facing counterclockwise.